& that would show all the records where ";4;" is common.
& you do run that in a loop, 1..80 > 1..80
then you'd have 80 files, named 1..80, where all records that contain ;#; are in that individual file

Knowing that you have 11676 lines in wyniki.csv (11675 records + 1 header),
you could run wc -l (word count -lines) on each of the output files & know that ;4; is found in 2614 records & ;80; is found in 1917 records...